1. Field of the Invention
The present invention relates to a fault diagnosis system which permits easy fault diagnosis of various automotive electronic devices.
Hitherto, fault diagnoses of electronic devices on automobiles have been conducted by connecting those devices to a tester via a pair of corresponding connectors which include a vehicle-side connector and a tester-side connector. The vehicle-side connector has a predetermined number of pins corresponding to the number of electronic devices and is connected to the electronic devices by a corresponding set of signal lines for transmitting therebetween signals representing the results of fault diagnosis of corresponding electronic devices and controlling signals from the tester. The tester-side connector also has a corresponding number of pins and is connected to the tester by another set of signal lines for transmitting therebetween the control signals from the tester and signals from the vehicle-side connector for display.
Consequently, if the number of electronic devices mounted in the automobile increases, the number of pins of both connectors must correspondingly be increased to accomodate the additional signal lines.
In addition, when the system of an electronic device has undergone a change, signals from the connector also undergo change, so that it sometimes becomes necessary to change the number of pins of the connectors and as well as alter the connections of the tester-side connector pins on each such occasion.
As a result, from a long-term perspective, compatible testers which ideally could be used for a wide variety of eleectronic fault diagnosis systems have not been available. Hence, it has been necessary to develop a special tester each time the fault diagnosis system changes. Accordingly there have been many wasteful factors such as different testers being prepared for different vehicle types and yearly model changes.
Next, a description will be made of a conventional fault diagnosis tester. FIG. 1 is a block diagram illustrating the configuration of a conventional fault diagnosis system. In FIG. 1, respective signal lines 9, 10, 11 and 12 are connected to a vehicle-side connector 5 from electronic devices 1, 2, 3, 4 which are control units for controlling various types of systems mounted on an automobile. In order to connect ON-OFF signals from the electronic devices 1, 2, 3 and 4 to a tester 7, a tester-side connector 6 which is connected to the tester 7 through signal lines 14, 15, 16 and 17 is connected to the vehicle-side connector 5. If a fault has occurred in any of the electronic devices 1 to 4, the result is diagnosed by the tester 7, and a code is displayed on a diplay 8 on the tester 7.
With the conventional fault diagnosis system, the electronic devices 1-4 are connected to each other as shown in FIG. 1. Thus, in cases where the number of systems is increased or a signaling system undergoes a change, it is necessary to change the number of pins at the vehicle-side connector 5 and the tester-side connector 6 for each such occasion. In addition, it is necessary to change the signal processing method of the tester 7 with respect to each terminal. Therefore, there have been drawbacks in that the testers become more specialized, pins must be rearranged or newly added, and that installation costs tend to become higher.